1. Field of the Invention
The present invention relates generally to a semiconductor memory device, and more particularly, but without limitation, to a phase-change memory device including a phase-change material pattern shared between adjacent cells.
2. Description of the Related Art
A phase-change memory device is a nonvolatile memory device using a phase-change material of which resistance varies according to the phase of the phase-change material. Each cell of a phase-change memory device includes a switching unit and a phase-change resistor electrically connected to the switching unit. The phase-change resistor includes a phase-change material pattern.
The phase-change material pattern is formed by patterning a phase-change material layer on an entire surface of a substrate. During the patterning process, the phase-change material pattern can be damaged. For example, edges of the phase-change material pattern can be deformed and/or can be changed in composition ratio. Particularly, when the phase-change material pattern includes separate islands for respective cells, the phase-change material pattern can be easily damaged since four sides of each island are exposed.